Instrumentation and methods for use in implanting a cervical disc replacement device

ABSTRACT

Instrumentation for implanting an intervertebral disc replacement device includes an insertion handle comprising a shaft having a proximal end and a distal end and an engagement member disposed at the distal end of the shaft and operable to detachably engage an insertion plate that maintains first and second members of an intervertebral disc replacement device in registration with one another for substantially simultaneous insertion into an intervertebral disc space of a spinal column. The invention also comprising a method for replacing at least a portion of an intervertebral disc in a spinal column, comprising the steps of removing the portion of the intervertebral disc from the spinal column and manipulating an insertion handle that is detachably engaged with an insertion plate that is coupled to first and second members of an intervertebral disc replacement device such that the first and second members may be substantially, simultaneously inserted into an intervertebral disc space of the spinal column, wherein the first and second members are engageable with and operable to permit the vertebral bones to articulate with respect to one another.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The application is a continuing application of U.S. patentapplication Ser. No. 10/688,632 (filed Oct. 17, 2003) entitled“Instrumentation and Methods for Use in Implanting a Cervical DiscReplacement Device” (“the '632 application”), which is a continuation inpart of U.S. patent application Ser. No. 10/382,702 (filed Mar. 6, 2003)entitled “Cervical Disc Replacement” (“the '702 application”), which'632 and '702 applications are hereby incorporated by reference hereinin their entireties.

FIELD OF THE INVENTION

[0002] This invention relates generally to systems and methods for usein spine arthroplasty, and more specifically to instruments forinserting and removing cervical disc replacement trials, and insertingand securing cervical disc replacement devices, and methods of usethereof.

BACKGROUND OF THE INVENTION

[0003] The structure of the intervertebral disc disposed between thecervical bones in the human spine comprises a peripheral fibrous shroud(the annulus) which circumscribes a spheroid of flexibly deformablematerial (the nucleus). The nucleus comprises a hydrophilic, elastomericcartilaginous substance that cushions and supports the separationbetween the bones while also permitting articulation of the twovertebral bones relative to one another to the extent such articulationis allowed by the other soft tissue and bony structures surrounding thedisc. The additional bony structures that define pathways of motion invarious modes include the posterior joints (the facets) and the lateralintervertebral joints (the unco-vertebral joints). Soft tissuecomponents, such as ligaments and tendons, constrain the overallsegmental motion as well.

[0004] Traumatic, genetic, and long term wearing phenomena contribute tothe degeneration of the nucleus in the human spine. This degeneration ofthis critical disc material, from the hydrated, elastomeric materialthat supports the separation and flexibility of the vertebral bones, toa flattened and inflexible state, has profound effects on the mobility(instability and limited ranges of appropriate motion) of the segment,and can cause significant pain to the individual suffering from thecondition. Although the specific causes of pain in patients sufferingfrom degenerative disc disease of the cervical spine have not beendefinitively established, it has been recognized that pain may be theresult of neurological implications (nerve fibers being compressed)and/or the subsequent degeneration of the surrounding tissues (thearthritic degeneration of the facet joints) as a result of their beingoverloaded.

[0005] Traditionally, the treatment of choice for physicians caring forpatients who suffer from significant degeneration of the cervicalintervertebral disc is to remove some, or all, of the damaged disc. Ininstances in which a sufficient portion of the intervertebral discmaterial is removed, or in which much of the necessary spacing betweenthe vertebrae has been lost (significant subsidence), restoration of theintervertebral separation is required.

[0006] Unfortunately, until the advent of spine arthroplasty devices,the only methods known to surgeons to maintain the necessary disc heightnecessitated the immobilization of the segment. Mobilization isgenerally achieved by attaching metal plates to the anterior orposterior elements of the cervical spine, and the insertion of someosteoconductive material (autograft, allograft, or other porousmaterial) between the adjacent vertebrae of the segment. Thisimmobilization and insertion of osteoconductive material has beenutilized in pursuit of a fusion of the bones, which is a procedurecarried out on tens of thousands of pain suffering patients per year.

[0007] This sacrifice of mobility at the immobilized, or fused, segment,however, is not without consequences. It was traditionally held that thepatient's surrounding joint segments would accommodate any additionalarticulation demanded of them during normal motion by virtue of thefused segment's immobility. While this is true over the short-term(provided only one, or at most two, segments have been fused), theeffects of this increased range of articulation demanded of theseadjacent segments has recently become a concern. Specifically, anincrease in the frequency of returning patients who suffer fromdegeneration at adjacent levels has been reported.

[0008] Whether this increase in adjacent level deterioration is trulyassociated with rigid fusion, or if it is simply a matter of theindividual patient's predisposition to degeneration is unknown. Eitherway, however, it is clear that a progressive fusion of a long sequenceof vertebrae is undesirable from the perspective of the patient'squality of life as well as from the perspective of pushing a patient toundergo multiple operative procedures.

[0009] While spine arthroplasty has been developing in theory over thepast several decades, and has even seen a number of early attempts inthe lumbar spine show promising results, it is only recently thatarthoplasty of the spine has become a truly realizable promise. Thefield of spine arthroplasty has several classes of devices. The mostpopular among these are: (a) the nucleus replacements, which arecharacterized by a flexible container filled with an elastomericmaterial that can mimic the healthy nucleus; and (b) the total discreplacements, which are designed with rigid endplates which house amechanical articulating structure that attempts to mimic and promote thehealthy segmental motion.

[0010] Among these solutions, the total disc replacements have begun tobe regarded as the most probable long-term treatments for patientshaving moderate to severe lumbar disc degeneration. In the cervicalspine, it is likely that these mechanical solutions will also become thetreatment of choice.

[0011] It is an object of the invention to provide instrumentation andmethods that enable surgeons to more accurately, easily, and efficientlyimplant fusion or non-fusion cervical disc replacement devices. Otherobjects of the invention not explicitly stated will be set forth andwill be more clearly understood in conjunction with the descriptions ofthe preferred embodiments disclosed hereafter.

SUMMARY OF THE INVENTION

[0012] The preceding objects are achieved by the invention, whichincludes cervical disc replacement trials, cervical disc replacementdevices, cervical disc replacement device insertion instrumentation(including, e.g., an insertion plate with mounting screws, an insertionhandle, and an insertion pusher), and cervical disc replacement devicefixation instrumentation (including, e.g., drill guides, drill bits,screwdrivers, bone screws, and retaining clips).

[0013] More particularly, the devices, instrumentation, and methodsdisclosed herein are intended for use in spine arthroplasty procedures,and specifically for use with the devices, instrumentation, and methodsdescribed herein in conjunction with the devices, instrumentation, andmethods described herein and in the '702 application. However, it shouldbe understood that the devices, instrumentation, and methods describedherein are also suitable for use with other intervertebral discreplacement devices, instrumentation, and methods without departing fromthe scope of the invention.

[0014] For example, while the trials described herein are primarilyintended for use in distracting an intervertebral space and/ordetermining the appropriate size of cervical disc replacement devices(e.g., described herein and in the '702 application) to be implanted (orwhether a particular size can be implanted) into the distractedintervertebral space, they can also be used for determining theappropriate size of any other suitably configured orthopedic implant ortrial to be implanted (or whether a particular size can be implanted)into the distracted intervertebral space. And, for example, while theinsertion instrumentation described herein is primarily intended for usein holding, inserting, and otherwise manipulating cervical discreplacement devices (e.g., described herein and, in suitably configuredembodiments, in the '702 application), it can also be used formanipulating any other suitably configured orthopedic implant or trial.And, for example, while the fixation instrumentation described herein isprimarily intended for use in securing within the intervertebral spacethe cervical disc replacement devices (e.g., described herein and, insuitably configured embodiments, in the '702 application), it can alsobe used with any other suitably configured orthopedic implant or trial.

[0015] While the instrumentation described herein (e.g., the trials,insertion instrumentation, and fixation instrumentation) will bediscussed for use with the cervical disc replacement device of FIGS.1a-3 f herein, such discussions are merely by way of example and notintended to be limiting of their uses. Thus, it should be understoodthat the tools can be used with suitably configured embodiments of thecervical disc replacement devices disclosed in the '702 application, orany other artificial intervertebral disc having (or being modifiable ormodified to have) suitable features therefor. Moreover, it isanticipated that the features of the cervical disc replacement device(e.g., the flanges, bone screw holes, and mounting holes) that are usedby the tools discussed herein to hold and/or manipulate these devices(some of such features, it should be noted, were first shown anddisclosed in the '702 application) can be applied, individually orcollectively or in various combinations, to other trials, spacers,artificial intervertebral discs, or other orthopedic devices asstand-alone innovative features for enabling such trials, spacers,artificial intervertebral discs, or other orthopedic devices to be moreefficiently and more effectively held and/or manipulated by the toolsdescribed herein or by other tools having suitable features. Inaddition, it should be understood that the invention encompassesartificial intervertebral discs, spacers, trials, and/or otherorthopedic devices, that have one or more of the features disclosedherein, in any combination, and that the invention is therefore notlimited to artificial intervertebral discs, spacers, trials, and/orother orthopedic devices having all of the features simultaneously.

[0016] The cervical disc replacement device of FIGS. 1a-3 f is analternate embodiment of the cervical disc replacement device of the '702application. The illustrated alternate embodiment of the cervical discreplacement device is identical in structure to the cervical discreplacement device in the '702 application, with the exception that thevertebral bone attachment flanges are configured differently, such thatthey are suitable for engagement by the instrumentation describedherein.

[0017] More particularly, in this alternate embodiment, the flange ofthe upper element extends upwardly from the anterior edge of the upperelement, and has a lateral curvature that approximates the curvature ofthe anterior periphery of the upper vertebral body against which it isto be secured. The attachment flange is provided with a flat recess,centered on the midline, that accommodates a clip of the presentinvention. The attachment flange is further provided with two bone screwholes symmetrically disposed on either side of the midline. The holeshave longitudinal axes directed along preferred bone screw drivinglines. Centrally between the bone screw holes, a mounting screw hole isprovided for attaching the upper element to an insertion plate of thepresent invention for implantation. The lower element is similarlyconfigured with a similar oppositely extending flange.

[0018] Once the surgeon has prepared the intervertebral space, thesurgeon may use one or more cervical disc replacement trials of thepresent invention to distract the intervertebral space and determine theappropriate size of a cervical disc replacement device to be implanted(or whether a particular size of the cervical disc replacement devicecan be implanted) into the distracted cervical intervertebral space.Preferably, for each cervical disc replacement device to be implanted, aplurality of sizes of the cervical disc replacement device would beavailable. Accordingly, preferably, each of the plurality of trials foruse with a particular plurality of differently sized cervical discreplacement devices would have a respective oval footprint and depthdimension set corresponding to the footprint and depth dimension set ofa respective one of the plurality of differently sized cervical discreplacement devices.

[0019] Each of the cervical disc replacement trials includes a distalend configured to approximate relevant dimensions of an availablecervical disc replacement device. The distal end has a head with an ovalfootprint. The upper surface of the head is convex, similar to theconfiguration of the vertebral body contact surface of the upper elementof the cervical disc replacement device (but without the teeth). Thelower surface of the head is flat, similar to the configuration of thevertebral body contact surface of the lower element of the cervical discreplacement device (but without the teeth). The cervical discreplacement trial, not having the teeth, can be inserted and removedfrom the intervertebral space without compromising the endplatesurfaces. The cervical disc replacement trial further has a vertebralbody stop disposed at the anterior edge of the head, to engage theanterior surface of the upper vertebral body before the trial isinserted too far into the intervertebral space.

[0020] Accordingly, the surgeon can insert and remove at least one ofthe trials (or more, as necessary) from the prepared intervertebralspace. As noted above, the trials are useful for distracting theprepared intervertebral space. For example, starting with the largestdistractor that can be wedged in between the vertebral bones, thesurgeon will insert the trial head and then lever the trial handle upand down to loosen the annulus and surrounding ligaments to urge thebone farther apart. The surgeon then removes the trial head from theintervertebral space, and replaces it with the next largest (in terms ofheight) trial head. The surgeon then levers the trial handle up and downto further loosen the annulus and ligaments. The surgeon then proceedsto remove and replace the trial head with the next largest (in terms ofheight) trial head, and continues in this manner with larger and largertrials until the intervertebral space is distracted to the appropriateheight.

[0021] Regardless of the distraction method used, the cervical discreplacement trials are useful for finding the cervical disc replacementdevice size that is most appropriate for the prepared intervertebralspace, because each of the trial heads approximates the relevantdimensions of an available cervical disc replacement device. Once theintervertebral space is distracted, the surgeon can insert and removeone or more of the trial heads to determine the appropriate size ofcervical disc replacement device to use. Once the appropriate size isdetermined, the surgeon proceeds to implant the selected cervical discreplacement device.

[0022] An insertion plate of the present invention is mounted to thecervical disc replacement device to facilitate a preferred simultaneousimplantation of the upper and lower elements of the replacement device.The upper and lower elements are held by the insertion plate in analigned configuration preferable for implantation. A ledge on the platemaintains a separation between the anterior portions of the inwardlyfacing surfaces of the elements to help establish and maintain thispreferred relationship. The flanges of the elements each have a mountingscrew hole and the insertion plate has two corresponding mounting holes.Mounting screws are secured through the colinear mounting screw holepairs, such that the elements are immovable with respect to theinsertion plate and with respect to one another. In this configuration,the upper element, lower element, and insertion plate construct ismanipulatable as a single unit.

[0023] An insertion handle of the present invention is providedprimarily for engaging an anteriorly extending stem of the insertionplate so that the cervical disc replacement device and insertion plateconstruct can be manipulated into and within the treatment site. Theinsertion handle has a shaft with a longitudinal bore at a distal endand a flange at a proximal end. Longitudinally aligning the insertionhandle shaft with the stem, and thereafter pushing the hollow distal endof the insertion handle shaft toward the insertion plate, causes thehollow distal end to friction-lock to the outer surface of the stem.Once the insertion handle is engaged with the insertion plate,manipulation of the insertion handle shaft effects manipulation of thecervical disc replacement device and insertion plate construct. Thesurgeon can therefore insert the construct into the treatment area. Moreparticularly, after the surgeon properly prepares the intervertebralspace, the surgeon inserts the cervical disc replacement device into theintervertebral space from an anterior approach, such that the upper andlower elements are inserted between the adjacent vertebral bones withthe element footprints fitting within the perimeter of theintervertebral space and with the teeth of the elements' vertebral bodycontact surfaces engaging the vertebral endplates, and with the flangesof the upper and lower elements flush against the anterior faces of theupper and lower vertebral bones, respectively.

[0024] Once the construct is properly positioned in the treatment area,the surgeon uses an insertion pusher of the present invention todisengage the insertion handle shaft from the stem of the insertionplate. The insertion pusher has a longitudinal shaft with a blunt distalend and a proximal end with a flange. The shaft of the insertion pushercan be inserted into and translated within the longitudinal bore of theinsertion handle shaft. Because the shaft of the insertion pusher is aslong as the longitudinal bore of the insertion handle shaft, the flangeof the insertion handle and the flange of the insertion pusher areseparated by a distance when the pusher shaft is inserted all the wayinto the longitudinal bore until the blunt distal end of the shaftcontacts the proximal face of the insertion plate stem. Accordingly, abringing together of the flanges (e.g., by the surgeon squeezing theflanges toward one another) will overcome the friction lock between thedistal end of the insertion handle shaft and the stem of the insertionplate.

[0025] Once the insertion handle has been removed, the surgeon uses adrill guide of the present invention to guide the surgeon's drilling ofbone screws through the bone screw holes of the upper and lowerelements' flanges and into the vertebral bones. The drill guide has alongitudinal shaft with a distal end configured with a central bore thataccommodates the stem so that the drill guide can be placed on andaligned with the stem. The distal end is further configured to have twoguide bores that have respective longitudinal axes at preferred bonescrew drilling paths relative to one another. When the central bore isdisposed on the stem of the insertion plate, the drill guide shaft canbe rotated on the stem into either of two preferred positions in whichthe guide bores are aligned with the bone screw holes on one of theflanges, or with the bone screw holes on the other flange.

[0026] To secure the upper element flange to the upper vertebral body,the surgeon places the drill guide shaft onto the stem of the insertionplate, and rotates the drill guide into the first preferred position.Using a suitable bone drill and cooperating drill bit, the surgeondrills upper tap holes for the upper bone screws. The surgeon thenrotates the drill guide shaft on the stem of the insertion plate untilthe guide bores no longer cover the upper bone screw holes. The surgeoncan then screw the upper bone screws into the upper tap holes using asuitable surgical bone screw driver. To then secure the lower elementflange to the lower vertebral body, the surgeon further rotates thedrill guide shaft on the stem of the insertion plate until the drillguide is in the second preferred position, and proceeds to drill thelower bone screw tap holes and screw the lower bone screws into them inthe same manner.

[0027] Once the upper and lower elements are secured to the adjacentvertebral bones, the surgeon removes the drill guide from the stem ofthe insertion plate and from the treatment area. Using a suitablesurgical screw driver, the surgeon then removes the mounting screws thathold the insertion plate against the elements' flanges and removes theinsertion plate and the mounting screws from the treatment area.

[0028] Once the mounting screws and the insertion plate are removed, thesurgeon uses a clip applicator of the present invention to mountretaining clips on the flanges to assist in retaining the bone screws.Each of the clips has a central attachment bore and, extendingtherefrom, a pair of oppositely directed laterally extending flanges andan upwardly (or downwardly) extending hooked flange. The clips can besnapped onto the element flanges (one clip onto each flange). Each ofthe laterally extending flanges of the clip is sized to cover at least aportion of a respective one of the bone screw heads when the clip isattached in this manner to the flange so that the clips help prevent thebone screws from backing out.

[0029] Also disclosed is an alternate dual cervical disc replacementdevice configuration suitable, for example, for implantation into twoadjacent cervical intervertebral spaces. The configuration includes analternate, upper, cervical disc replacement device (including an upperelement and an alternate lower element), for implantation into an uppercervical intervertebral space, and further includes an alternate, lower,cervical disc replacement device (including an alternate upper elementand a lower element), for implantation into an adjacent, lower, cervicalintervertebral space. The illustrated alternate, upper, embodiment isidentical in structure to the cervical disc replacement device of FIGS.1a-3 f, with the exception that the flange of the lower element isconfigured differently and without bone screw holes. The illustratedalternate, lower, embodiment is identical in structure to the cervicaldisc replacement device of FIGS. 1a-3 f, with the exception that theflange of the upper element is configured differently and without bonescrew holes.

[0030] More particularly, in the alternate, upper, cervical discreplacement device of this alternate configuration, the flange of thealternate lower element does not have bone screw holes, but does have amounting screw hole for attaching the alternate lower element to analternate, upper, insertion plate. Similarly, in the alternate, lower,cervical disc replacement device of this alternate configuration, theflange of the alternate upper element does not have bone screw holes,but does have a mounting screw hole for attaching the alternate upperelement to an alternate, lower, insertion plate. The extent of theflange of the alternate lower element is laterally offset to the right(in an anterior view) from the midline, and the extent of the flange ofthe alternate upper element is laterally offset to the left (in ananterior view) from the midline, so that the flanges avoid one anotherwhen the alternate lower element of the alternate, upper, cervical discreplacement device, and the alternate upper element of the alternate,lower, cervical disc replacement device, are implanted in this alternateconfiguration.

[0031] The alternate, upper, insertion plate is identical in structureto the insertion plate described above, with the exception that thelower flange is offset from the midline (to the right in an anteriorview) to align its mounting screw hole with the offset mounting screwhole of the alternate lower element. Similarly, the alternate, lower,insertion plate is identical in structure to the insertion platedescribed above, with the exception that the upper flange is offset fromthe midline (to the left in an anterior view) to align its mountingscrew hole with the offset mounting screw hole of the alternate upperelement.

[0032] Accordingly, the upper and lower elements of the alternate,upper, cervical disc replacement device, being held by the alternateupper insertion plate, as well as the upper and lower elements of thealternate, lower, cervical disc replacement device, being held by thealternate lower insertion plate, can be implanted using the insertionhandle, insertion pusher, drill guide, clips (one on the uppermostelement flange, and one on the lowermost element flange, because onlythe uppermost element and the lowermost element are secured by bonescrews), and clip applicator, in the manner described above with respectto the implantation of the cervical disc replacement device.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033]FIGS. 1a-c show anterior (FIG. 1a), lateral (FIG. 1b), and bottom(FIG. 1c) views of a top element of a cervical disc replacement deviceof the invention.

[0034]FIGS. 2a-c show anterior (FIG. 2a), lateral (FIG. 2b), and top(FIG. 2c) views of a bottom element of the cervical disc replacementdevice.

[0035]FIG. 3a-f show top (FIG. 3a), lateral (FIG. 3b), anterior (FIG.3c), posterior (FIG. 3d), antero-lateral perspective (FIG. 3e), andpostero-lateral perspective (FIG. 3f) views of the cervical discreplacement device, assembled with the top and bottom elements of FIGS.1a-c and 2 a-c.

[0036]FIGS. 4a-g show top (FIG. 4a), lateral (FIG. 4b), anterior (FIG.4c), posterior (FIG. 4d), antero-lateral perspective (head only) (FIG.4e), and postero-lateral perspective (head only) (FIG. 4f) views of acervical disc replacement trial of the present invention.

[0037]FIGS. 5a-d show top (FIG. 5a), lateral (FIG. 5b), anterior (FIG.5c), and posterior (FIG. 5d) views of an insertion plate of theinsertion instrumentation of the present invention. FIGS. 5e and 5 fshow anterior (FIG. 5e) and antero-lateral perspective (FIG. 5f) viewsof the insertion plate mounted to the cervical disc replacement device.

[0038]FIGS. 6a-d show top (FIG. 6a), lateral (FIG. 6b), anterior (FIG.6c), and postero-lateral (FIG. 6d) views of an insertion handle of theinsertion instrumentation of the present invention. FIG. 6e shows anantero-lateral perspective view of the insertion handle attached to theinsertion plate. FIG. 6f shows a magnified view of the distal end ofFIG. 6e.

[0039]FIGS. 7a-c show top (FIG. 7a), lateral (FIG. 7b), and anterior(FIG. 7c) views of an insertion pusher of the insertion instrumentationof the present invention. FIG. 7d shows an antero-lateral perspectiveview of the insertion pusher inserted into the insertion handle. FIG. 7eshows a magnified view of the proximal end of FIG. 7d.

[0040]FIGS. 8a-c show top (FIG. 8a), lateral (FIG. 8b), and anterior(FIG. 8c) views of a drill guide of the insertion instrumentation of thepresent invention. FIG. 8d shows an antero-lateral perspective view ofthe drill guide inserted onto the insertion plate. FIG. 8e shows amagnified view of the distal end of FIG. 8d.

[0041]FIG. 9a shows an antero-lateral perspective view of the cervicaldisc replacement device implantation after bone screws have been appliedand before the insertion plate has been removed. FIG. 9b shows anantero-lateral perspective view of the cervical disc replacement deviceafter bone screws have been applied and after the insertion plate hasbeen removed.

[0042]FIGS. 10a-f show top (FIG. 10a), lateral (FIG. 10b), posterior(FIG. 10c), anterior (FIG. 10d), postero-lateral (FIG. 10e), andantero-lateral (FIG. 10f) views of a retaining clip of the presentinvention.

[0043]FIGS. 11a-c show top (FIG. 11a), lateral (FIG. 11b), and anterior(FIG. 11c) views of a clip applicator of the insertion instrumentationof the present invention. FIG. 11d shows a postero-lateral perspectiveview of the clip applicator holding two retaining clips. FIG. 11e showsan antero-lateral perspective view of FIG. 11d.

[0044]FIG. 12a shows the clip applicator applying the retaining clips tothe cervical disc replacement device. FIGS. 12b-h show anterior (FIG.12b), posterior (FIG. 12c), top (FIG. 12d), bottom (FIG. 12e), lateral(FIG. 12f), antero-lateral perspective (FIG. 12g), and postero-lateralperspective (FIG. 12h) views of the cervical disc replacement deviceafter the retaining clips have been applied.

[0045]FIGS. 13a-b show a prior art one level cervical fusion plate inanterior (FIG. 13a) and lateral (FIG. 13b) views. FIGS. 13c-d show aprior art two level cervical fusion plate in anterior (FIG. 13c) andlateral (FIG. 13d) views.

[0046]FIGS. 14a-e show an alternate, dual cervical disc replacementdevice configuration and alternate insertion plates for use therewith,in exploded perspective (FIG. 14a), anterior (FIG. 14b), posterior (FIG.14c), lateral (FIG. 14d), and collapsed perspective (FIG. 14e) views.

[0047]FIGS. 15a-c show an alternate upper element of the configurationof FIGS. 14a-e, in posterior (FIG. 15a), anterior (FIG. 15b), andantero-lateral (FIG. 15c) views.

[0048]FIGS. 16a-c show an alternate lower element of the configurationof FIGS. 14a-e, in posterior (FIG. 16a), anterior (FIG. 16b), andantero-lateral (FIG. 16c) views.

[0049]FIGS. 17a-c show an alternate, upper, insertion plate of theconfiguration of FIGS. 14a-e in anterior (FIG. 17a), posterior (FIG.17b), and antero-lateral (FIG. 17c) views.

[0050]FIGS. 18a-c show an alternate, lower, insertion plate of theconfiguration of FIGS. 14a-e in anterior (FIG. 18a), posterior (FIG.18b), and antero-lateral (FIG. 18c) views.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0051] While the invention will be described more fully hereinafter withreference to the accompanying drawings, it is to be understood at theoutset that persons skilled in the art may modify the invention hereindescribed while achieving the functions and results of the invention.Accordingly, the descriptions that follow are to be understood asillustrative and exemplary of specific structures, aspects and featureswithin the broad scope of the invention and not as limiting of suchbroad scope. Like numbers refer to similar features of like elementsthroughout.

[0052] A preferred embodiment of a cervical disc replacement device ofthe present invention, for use with the instrumentation of the presentinvention, will now be described.

[0053] Referring now to FIGS. 1a-3 f, a top element 500 of the cervicaldisc replacement device 400 is shown in anterior (FIG. 1a), lateral(FIG. 1b), and bottom (FIG. 1c) views; a bottom element 600 of thecervical disc replacement device 400 is shown in anterior (FIG. 2a),lateral (FIG. 2b), and top (FIG. 2c) views; and an assembly 400 of thetop and bottom elements 500,600 is shown in top (FIG. 3a), lateral (FIG.3b), anterior (FIG. 3c), posterior (FIG. 3d), antero-lateral perspective(FIG. 3e), and postero-lateral perspective (FIG. 3f) views.

[0054] The cervical disc replacement device 400 is an alternateembodiment of the cervical disc replacement device of the '702application. The illustrated alternate embodiment of the cervical discreplacement device is identical in structure to the cervical discreplacement device 100 in the '702 application (and thus like componentsare like numbered, but in the 400s rather than the 100s, in the 500srather than the 200s, and in the 600s rather than the 300s), with theexception that the vertebral bone attachment flanges are configureddifferently, such that they are suitable for engagement by theinstrumentation described herein. (It should be noted that, while the'702 application illustrated and described the cervical disc replacementdevice 100 as having an upper element flange 506 with two bone screwholes 508 a,508 b, and a lower element flange 606 with one bone screwhole 608, the '702 application explained that the number of holes andthe configuration of the flanges could be modified without departingfrom the scope of the invention as described in the '702 application.)

[0055] More particularly, in this alternate embodiment, the upperelement 500 of the cervical disc replacement device 400 has a vertebralbody attachment structure (e.g., a flange) 506 that preferably extendsupwardly from the anterior edge of the upper element 500, and preferablyhas a lateral curvature that approximates the curvature of the anteriorperiphery of the upper vertebral body against which it is to be secured.The attachment flange 506 is preferably provided with a flat recess 507,centered on the midline, that accommodates a clip 1150 a (describedbelow) of the present invention. The attachment flange 506 is furtherprovided with at least one (e.g., two) bone screw holes 508 a,508 b,preferably symmetrically disposed on either side of the midline.Preferably, the holes 508 a,508 b have longitudinal axes directed alongpreferred bone screw driving lines. For example, in this alternateembodiment, the preferred bone screw driving lines are angled upwardlyat 5 degrees and inwardly (toward one another) at 7 degrees (a total of14 degrees of convergence), to facilitate a toenailing of the bonescrews (described below and shown in FIGS. 12a-h). Centrally between thebone screw holes 508 a,508 b, at least one mounting feature (e.g., amounting screw hole) 509 is provided for attaching the upper element 500to an insertion plate 700 (described below) for implantation.

[0056] Similarly, in this alternate embodiment, the lower element 600 ofthe cervical disc replacement device 400 also has a vertebral bodyattachment structure (e.g., an oppositely directed and similarlyconfigured vertebral body attachment flange) 606 that preferably extendsdownwardly from the anterior edge of the lower element 600, andpreferably has a lateral curvature that approximates the curvature ofthe anterior periphery of the lower vertebral body against which it isto be secured. The attachment flange 606 is preferably provided with aflat recess 607, centered on the midline, that accommodates a clip 1150b (described below) of the present invention. The attachment flange 606is further provided with at least one (e.g., two) bone screw holes 608a,608 b, preferably symmetrically disposed on either side of themidline. Preferably, the holes 608 a,608 b have longitudinal axesdirected along preferred bone screw driving lines. For example, in thisalternate embodiment, the preferred bone screw driving lines are angleddownwardly at 5 degrees and inwardly (toward one another) at 7 degrees(a total of 14 degrees of convergence), to facilitate a toenailing ofthe bone screws (described below and shown in FIGS. 12a-h). Centrallybetween the bone screw holes 608 a,608 b, at least one mounting feature(e.g., a mounting screw hole) 609 is provided for attaching the lowerelement 600 to the insertion plate 700 (described below) forimplantation.

[0057] Prior to implantation of the cervical disc replacement device,the surgeon will prepare the intervertebral space. Typically, this willinvolve establishing access to the treatment site, removing the damagednatural intervertebral disc, preparing the surfaces of the endplates ofthe vertebral bones adjacent the intervertebral space, and distractingthe intervertebral space. (It should be noted that the cervical discreplacement device of the present invention, and the instrumentation andimplantation methods described herein, require minimal if any endplatepreparation.) More particularly, after establishing access to thetreatment site, the surgeon will remove the natural disc material,preferably leaving as much as possible of the annulus intact. Then, thesurgeon will remove the anterior osteophyte that overhangs the mouth ofthe cervical intervertebral space, and any lateral osteophytes that mayinterfere with the placement of the cervical disc replacement device orthe movement of the joint. Using a burr tool, the surgeon will thenensure that the natural lateral curvature of the anterior faces of thevertebral bodies is uniform, by removing any surface anomalies thatdeviate from the curvature. Also using the burr tool, the surgeon willensure that the natural curvature of the endplate surface of the uppervertebral body, and the natural flatness of the endplate surface of thelower vertebral body, are uniform, by removing any surface anomaliesthat deviate from the curvature or the flatness. Thereafter, the surgeonwill distract the intervertebral space to the appropriate height forreceiving the cervical disc replacement device. Any distraction tool ormethod known in the art, e.g., a Caspar Distractor, can be used toeffect the distraction and/or hold open the intervertebral space.Additionally or alternatively, the cervical disc replacement trials ofthe present invention can be used to distract the intervertebral space(as described below).

[0058] Referring now to FIGS. 4a-f, a cervical disc replacement trial1200 of the present invention is shown in top (FIG. 4a), lateral (FIG.4b), lateral (head only) (FIG. 4c), posterior (FIG. 4d), anterior (FIG.4e), antero-lateral perspective (head only) (FIG. 4f), andpostero-lateral perspective (head only) (FIG. 4g) views.

[0059] Preferably, a plurality of cervical disc replacement trials areprovided primarily for use in determining the appropriate size of acervical disc replacement device to be implanted (or whether aparticular size of the cervical disc replacement device can beimplanted) into the distracted cervical intervertebral space (e.g., thecervical disc replacement device 400 of FIGS. 1a-3 f). Preferably, foreach cervical disc replacement device to be implanted, a plurality ofsizes of the cervical disc replacement device would be available. Thatis, preferably, a plurality of the same type of cervical discreplacement device would be available, each of the plurality having arespective footprint and depth dimension combination that allows it tofit within a correspondingly dimensioned intervertebral space. Forexample, the plurality of cervical disc replacement devices couldinclude cervical disc replacement devices having oval footprints being12 mm by 14 mm, 14 mm by 16 mm, or 16 mm by 18 mm, and depths rangingfrom 6 mm to 14 mm in 1 mm increments, for a total of 27 devices.Accordingly, preferably, each of the plurality of trials for use with aparticular plurality of differently sized cervical disc replacementdevices would have a respective oval footprint and depth dimension setcorresponding to the footprint and depth dimension set of a respectiveone of the plurality of differently sized cervical disc replacementdevices. For example, the plurality of trials for use with the set ofcervical disc replacement devices described, for example, could includetrials having oval footprints being 12 mm by 14 mm, 14 mm by 16 mm, or16 mm by 18 mm, and depths ranging from 6 mm to 14 mm in 1 mmincrements, for a total of 27 static trials. It should be understoodthat the cervical disc replacement devices and/or the trials can beoffered in a variety of dimensions without departing from the scope ofthe invention, and that the dimensions specifically identified andquantified herein are merely exemplary. Moreover, it should beunderstood that the set of trials need not include the same number oftrials for each cervical disc replacement device in the set of cervicaldisc replacement devices, but rather, none, one, or more than one trialcan be included in the trial set for any particular cervical discreplacement device in the set.

[0060] Each of the cervical disc replacement trials (the cervical discreplacement trial 1200 shown in FIGS. 4a-g is exemplary for all of thetrials in the plurality of trials; preferably the trials in theplurality of trials differ from one another only with regard to certaindimensions as described above) includes a shaft 1202 having a configureddistal end 1204 and a proximal end having a handle 1206. Preferably, theproximal end is provided with a manipulation features (e.g., a hole1216) to, e.g., decrease the weight of the trial 1200, facilitatemanipulation of the trial 1200, and provide a feature for engagement byan instrument tray protrusion. The distal end is configured toapproximate relevant dimensions of the cervical disc replacement device.More particularly in the illustrated embodiment (for example), thedistal end 1204 has a trial configuration (e.g., a head 1208 having anoval footprint dimensioned at 12 mm by 14 mm, and a thickness of 6 mm).The upper surface 1210 of the head 1208 is convex, similar to theconfiguration of the vertebral body contact surface of the upper element500 of the cervical disc replacement device 400 (but without the teeth).The lower surface 1212 of the head 1208 is flat, similar to theconfiguration of the vertebral body contact surface of the lower element600 of the cervical disc replacement device 400 (but without the teeth).The illustrated embodiment, therefore, with these dimensions,approximates the size of a cervical disc replacement device having thesame height and footprint dimensions. The cervical disc replacementtrial, not having the teeth, can be inserted and removed from theintervertebral space without compromising the endplate surfaces. Thecervical disc replacement trial 1200 further has an over-insertionprevention features (e.g., a vertebral body stop 1214) preferablydisposed at the anterior edge of the head 1208, to engage the anteriorsurface of the upper vertebral body before the trial 1200 is insertedtoo far into the intervertebral space. The body of the trial 1200preferably has one or more structural support features (e.g., a rib 1216extending anteriorly from the head 1208 below the shaft 1202) thatprovides stability, e.g., to the shaft 1202 for upward and downwardmovement, e.g., if the head 1208 must be urged into the intervertebralspace by moving the shaft 1202 in this manner. Further, preferably asshown, the head 1208 is provided with an insertion facilitation features(e.g., a taper, decreasing posteriorly) to facilitate insertion of thehead 1208 into the intervertebral space by, e.g., acting as a wedge tourge the vertebral endplates apart. Preferably, as shown, the uppersurface 1210 is fully tapered at approximately 5 degrees, and the distalhalf of the lower surface 1212 is tapered at approximately 4 degrees.

[0061] Accordingly, the surgeon can insert and remove at least one ofthe trials (or more, as necessary) from the prepared intervertebralspace. As noted above, the trials are useful for distracting theprepared intervertebral space. For example, starting with the largestdistractor that can be wedged in between the vertebral bones, thesurgeon will insert the trial head 1208 (the tapering of the trial head1208 facilitates this insertion by acting as a wedge to urge thevertebral endplates apart), and then lever the trial handle 1206 up anddown to loosen the annulus and surrounding ligaments to urge the bonefarther apart. Once the annulus and ligaments have been loosened, thesurgeon removes the trial head 1208 from the intervertebral space, andreplaces it with the next largest (in terms of height) trial head 1208.The surgeon then levers the trial handle 1206 up and down to furtherloosen the annulus and ligaments. The surgeon then proceeds to removeand replace the trial head 1208 with the next largest (in terms ofheight) trial head 1208, and continues in this manner with larger andlarger trials until the intervertebral space is distracted to theappropriate height. This gradual distraction method causes thedistracted intervertebral space to remain at the distracted height withminimal subsidence before the cervical disc replacement device isimplanted. The appropriate height is one that maximizes the height ofthe intervertebral space while preserving the annulus and ligaments.

[0062] Regardless of the distraction method used, the cervical discreplacement trials are useful for finding the cervical disc replacementdevice size that is most appropriate for the prepared intervertebralspace, because each of the trial heads approximates the relevantdimensions of an available cervical disc replacement device. Once theintervertebral space is distracted, the surgeon can insert and removeone or more of the trial heads to determine the appropriate size ofcervical disc replacement device to use. Once the appropriate size isdetermined, the surgeon proceeds to implant the selected cervical discreplacement device.

[0063] A preferred method of, and instruments for use in, implanting thecervical disc replacement device will now be described.

[0064] Referring now to FIGS. 5a-f, an insertion plate 700 of theinsertion instrumentation of the present invention is shown in top (FIG.5a), lateral (FIG. 5b), anterior (FIG. 5c), and posterior (FIG. 5d)views. FIGS. 5e and 5 f show anterior (FIG. 5e) and antero-lateralperspective (FIG. 5f) views of the insertion plate 700 mounted to thecervical disc replacement device 400.

[0065] The insertion plate 700 has a base 702 with a first mounting area704 a (preferably an upwardly extending flange) and a second mountingarea 704 b (preferably a downwardly extending flange), and a primaryattachment feature (e.g., an anteriorly extending central stem) 706. Theconnection of the stem 706 to the base 702 preferably includes an axialrotation prevention feature, e.g., two oppositely and laterallyextending key flanges 708 a,708 b. The stem 706 preferably has aproximal portion 710 that is tapered to have a decreasing diameter awayfrom the base 702. That is, the tapered proximal portion 710 has aninitial smaller diameter that increases toward the base 702 gradually toa final larger diameter. The base 702 preferably has a posteriorlyextending ledge 716 that has a flat upper surface and a curved lowersurface.

[0066] The insertion plate 700 is mounted to the cervical discreplacement device 400 to facilitate the preferred simultaneousimplantation of the upper and lower elements 500,600. The upper andlower elements 500,600 are held by the insertion plate 700 in apreferred relationship to one another that is suitable for implantation.More particularly, as shown in FIGS. 3a-f, 5 e, and 5 f, the elements500,600 are preferably axially rotationally aligned with one another,with the element perimeters and flanges 506,606 axially aligned with oneanother, and held with the bearing surfaces 512,612 in contact. Theledge 716 maintains a separation between the anterior portions of theinwardly facing surfaces of the elements 500,600 to help establish andmaintain this preferred relationship, with the flat upper surface of theledge 716 in contact with the flat anterior portion of the inwardlyfacing surface of the upper element 500, and the curved lower surface ofthe ledge 716 in contact with the curved anterior portion of theinwardly facing surface of the lower element 600.

[0067] While any suitable method or mechanism can be used to mount theelements 500,600 to the insertion plate 700, a preferred arrangement isdescribed. That is, it is preferred, as shown and as noted above, thatthe flanges 506,606 of the elements 500,600 (in addition to having thebone screw holes 508 a,508 b,608 a,608 b described above) each have atleast one mounting feature (e.g., mounting screw hole 509,609), and theinsertion plate 700 has two (at least two, each one alignable with arespective mounting screw hole 509,609) corresponding mounting features(e.g., mounting screw holes 712 a,712 b), spaced to match the spacing of(and each be colinear with a respective one of) the mounting screw holes509,609 on the flanges 506,606 of the elements 500,600 of the cervicaldisc replacement device 400 when those elements 500,600 are disposed inthe preferred relationship for implantation. Accordingly, mountingscrews 714 a,714 b or other suitable fixation devices are securedthrough the colinear mounting screw hole pairs 509,712 a and 609,712 b(one screw through each pair), such that the elements 500,600 areimmovable with respect to the insertion plate 700 and with respect toone another. Thus, in this configuration, the upper element 500, lowerelement 600, and insertion plate 700 construct is manipulatable as asingle unit.

[0068] Preferably, for each size of cervical disc replacement device,the described configuration is established (and rendered sterile in ablister pack through methods known in the art) prior to delivery to thesurgeon. That is, as described below, the surgeon will simply need toopen the blister pack and apply the additional implantation tools to theconstruct in order to implant the cervical disc replacement device.Preferably, the configuration or dimensions of the insertion plate canbe modified (either by providing multiple different insertion plates, orproviding a single dynamically modifiable insertion plate) toaccommodate cervical disc replacement devices of varying heights. Forexample, the positions of the mounting screw holes 712 a,712 b on theflanges 704 a,704 b can be adjusted (e.g., farther apart for replacementdevices of greater height, and close together for replacement devices oflesser height), and the size of the flanges 704 a,70 b can be adjustedto provide structural stability for the new hole positions. Preferably,in other respects, the insertion plate configuration and dimensions neednot be modified, to facilitate ease of manufacturing and lowermanufacturing costs.

[0069] It should be noted that the described configuration of theconstruct presents the cervical disc replacement device to the surgeonin a familiar manner. That is, by way of explanation, current cervicalfusion surgery involves placing a fusion device (e.g., bone or a porouscage) in between the cervical intervertebral bones, and attaching acervical fusion plate to the anterior aspects of the bones. Widely usedcervical fusion devices (an example single level fusion plate 1300 isshown in anterior view in FIG. 13a and in lateral view in FIG. 13b) areconfigured with a pair of laterally spaced bone screw holes 1302 a,1302b on an upper end 1304 of the plate 1300, and a pair of laterally spacedbone screw holes 1306 a,1306 b on a lower end 1308 of the plate 1300. Toattach the plate 1300 to the bones, two bone screws are disposed throughthe upper end's bone screw holes 1302 a,1302 b and into the upper bone,and two bone screws are disposed through the lower end's bone screwholes 1306 a,1306 b and into the lower bone. This prevents the bonesfrom moving relative to one another, and allows the bones to fuse to oneanother with the aid of the fusion device.

[0070] Accordingly, as can be seen in FIG. 5e, when the upper and lowerelements 500,600 of the cervical disc replacement device 400 are held inthe preferred spatial relationship, the flanges 506,606 of the elements500,600, and their bone screw holes 508 a,508 b, present to the surgeona cervical hardware and bone screw hole configuration similar to afamiliar cervical fusion plate configuration. The mounting of theelements 500,600 to the insertion plate 700 allows the elements 500,600to be manipulated as a single unit for implantation (by manipulating theinsertion plate 700), similar to the way a cervical fusion plate ismanipulatable as a single unit for attachment to the bones. This aspectof the present invention simplifies and streamlines the cervical discreplacement device implantation procedure.

[0071] As noted above, the cervical disc replacement device 400 andinsertion plate 700 construct is preferably provided sterile (e.g., in ablister pack) to the surgeon in an implant tray (the tray preferablybeing filled with constructs for each size of cervical disc replacementdevice). The construct is preferably situated in the implant tray withthe stem 706 of the insertion plate 700 facing upwards for readyacceptance of the insertion handle 800 (described below).

[0072] Referring now to FIGS. 6a-e, an insertion handle 800 of theinsertion instrumentation of the present invention is shown in top (FIG.6a), lateral (FIG. 6b), anterior (FIG. 6c), and postero-lateral (distalend only) (FIG. 6d) views. FIG. 6e shows an antero-lateral perspectiveview of the insertion handle 800 attached to the stem 706 of theinsertion plate 700. FIG. 6f shows a magnified view of the distal end ofFIG. 6e.

[0073] The insertion handle 800 is provided primarily for engaging thestem 706 of the insertion plate 700 so that the cervical discreplacement device 400 and insertion plate 700 construct can bemanipulated into and within the treatment site. The insertion handle 800has a shaft 802 with an attachment feature (e.g., a longitudinal bore)804 at a distal end 806 and a manipulation feature (e.g., a flange) 810at a proximal end 808. Preferably, the longitudinal bore 804 has aninner taper at the distal end 806 such that the inner diameter of thedistal end 806 decreases toward the distal end 806, from an initiallarger inner diameter at a proximal portion of the distal end 806 to afinal smaller inner diameter at the distal edge of the distal end 806.The distal end 806 also preferably has an axial rotation preventionfeature, e.g., two (at least one) key slots 814 a,814 b extendingproximally from the distal end 806. Each slot 814 a,814 b is shaped toaccommodate the key flanges 708 a,708 b at the connection of the base702 to the stem 706 when the distal end 806 is engaged with the stem706. The material from which the insertion handle 800 is formed(preferably, e.g., Ultem™), and also the presence of the key slots 814a,814 b, permits the diameter of the hollow distal end 806 to expand asneeded to engage the tapered stem 706 of the insertion plate 700. Moreparticularly, the resting diameter (prior to any expansion) of thehollow distal end 806 of the insertion handle 800 is incrementallylarger than the initial diameter of the tapered proximal portion 710 ofthe stem 706 of the insertion plate 700, and incrementally smaller thanthe final diameter of the tapered proximal portion 710 of the stem 706of the insertion plate 700. Accordingly, longitudinally aligning theinsertion handle shaft 802 with the stem 706, and thereafter pushing thehollow distal end 806 of the insertion handle shaft 802 toward theinsertion plate 700, causes the hollow distal end 806 to initiallyreadily encompass the tapered proximal portion 710 of the stem 706(because the initial diameter of the tapered proximal portion 710 issmaller than the resting diameter of the hollow tapered distal end 806).With continued movement of the insertion handle shaft 802 toward theinsertion plate base 702, the hollow distal end 806 is confronted by theincreasing diameter of the tapered proximal portion 710. Accordingly,the diameter of the hollow distal end 806 expands (by permission of theshaft 802 body material and the key slots 814 a,814 b as the slotsnarrow) under the confrontation to accept the increasing diameter.Eventually, with continued movement under force, the inner surface ofthe hollow distal end 806 is friction-locked to the outer surface of thetapered proximal portion 710. Each of the key slots 814 a,814 bstraddles a respective one of the key flanges 708 a,708 b at theconnection of the base 702 to the stem 706. This enhances the ability ofthe insertion handle 800 to prevent rotation of the insertion handleshaft 802 relative to the insertion plate 700 (about the longitudinalaxis of the insertion handle shaft 802). It should be understood thatother methods or mechanisms of establishing engagement of the stem 706by the insertion handle 800 can be used without departing from the scopeof the invention.

[0074] Once the insertion handle 800 is engaged with the insertion plate700, manipulation of the insertion handle shaft 802 effects manipulationof the cervical disc replacement device 400 and insertion plate 700construct. The surgeon can therefore remove the construct from theimplant tray, and insert the construct into the treatment area. Moreparticularly, according to the implantation procedure of the invention,after the surgeon properly prepares the intervertebral space (removesthe damaged natural disc, modifies the bone surfaces that define theintervertebral space, and distracts the intervertebral space to theappropriate height), the surgeon inserts the cervical disc replacementdevice 400 into the intervertebral space from an anterior approach, suchthat the upper and lower elements 500,600 are inserted between theadjacent vertebral bones with the element footprints fitting within theperimeter of the intervertebral space and with the teeth of theelements' vertebral body contact surfaces 502,602 engaging the vertebralendplates, and with the flanges 506,606 of the upper and lower elements500,600 flush against the anterior faces of the upper and lowervertebral bones, respectively. (As discussed above, the flanges 506,606preferably have a lateral curvature that approximates the lateralcurvature of the anterior faces of the vertebral bones.)

[0075] Referring now to FIGS. 7a-e, an insertion pusher 900 of theinsertion instrumentation of the present invention is shown in top (FIG.7a), lateral (FIG. 7b), and anterior (FIG. 7c) views. FIG. 7d shows anantero-lateral perspective view of the insertion pusher 900 insertedinto the insertion handle 800. FIG. 7e shows a magnified view of theproximal end of FIG. 7d.

[0076] Once the construct is properly positioned in the treatment area,the surgeon uses the insertion pusher 900 to disengage the insertionhandle shaft 802 from the stem 706 of the insertion plate 700. Moreparticularly, the insertion pusher 900 has a longitudinal shaft 902having a preferably blunt distal end 904 and a proximal end 906preferably having a flange 908. The shaft 902 of the insertion pusher900 has a diameter smaller than the inner diameter of the insertionhandle shaft 802, such that the shaft 902 of the insertion pusher 900can be inserted into and translated within the longitudinal bore 804 ofthe insertion handle shaft 802. (The longitudinal bore 804 preferably,for the purpose of accommodating the insertion pusher 900 and otherpurposes, extends the length of the insertion handle shaft 802.) Theshaft 902 of the insertion pusher 900 is preferably as long as (or,e.g., at least as long as) the longitudinal bore 804. Accordingly, toremove the insertion handle shaft 802 from the insertion plate 700, theshaft 902 of the insertion pusher 900 is inserted into the longitudinalbore 804 of the insertion handle shaft 802 and translated therein untilthe blunt distal end 904 of the pusher shaft 802 is against the proximalend of the tapered stem 7.06 of the insertion plate 700. Because theshaft 902 of the insertion pusher 900 is as long as the longitudinalbore 804 of the insertion handle shaft 802, the flange 810 of theinsertion handle 800 and the flange 908 of the insertion pusher 900 areseparated by a distance (see FIGS. 7d and 7 e) that is equivalent to thelength of that portion of the stem 706 that is locked in the distal end806 of the insertion handle shaft 802. Accordingly, a bringing togetherof the flanges 810,908 (e.g., by the surgeon squeezing the flanges810,908 toward one another) will overcome the friction lock between thedistal end 806 of the insertion handle shaft 802 and the stem 706 of theinsertion plate 700, disengaging the insertion handle shaft 802 from theinsertion plate 700 without disturbing the disposition of the cervicaldisc replacement device 400 and insertion plate 700 construct in thetreatment area.

[0077] Referring now to FIGS. 8a-e, a drill guide 1000 of the insertioninstrumentation of the present invention is shown in top (FIG. 8a),lateral (FIG. 8b), and anterior (FIG. 8c) views. FIG. 8d shows anantero-lateral perspective view of the drill guide 1000 inserted ontothe stem 706 of the insertion plate 700. FIG. 8e shows a magnified viewof the distal end of FIG. 8d.

[0078] Once the insertion handle 800 has been removed, the surgeon usesthe drill guide 1000 to guide the surgeon's drilling of the bone screws(described below) through the bone screw holes 508 a,508 b and 608 a,608b of the upper 500 and lower 600 elements' flanges 506,606 and into thevertebral bones. More particularly, the drill guide 1000 has alongitudinal shaft 1002 having a configured distal end 1004 and aproximal end 1006 with a manipulation feature (e.g., lateral extensions1008 a,1008 b). The lateral extensions 1008 a,1008 b are useful formanipulating the shaft 1002. The distal end 1004 is configured to have ashaft guiding feature (e.g., a central bore 1010) suitable for guidingthe shaft 1002 in relation to the stem 706 of the insertion plate 700therethrough. For example, the central bore 1010 accommodates the stem706 so that the drill guide 1000 can be placed on and aligned with thestem 706. The longitudinal axis of the bore 1010 is preferably offsetfrom the longitudinal axis of the drill guide shaft 1002. The distal end1004 is further configured to have two guide bores 1012 a,1012 b thathave respective longitudinal axes at preferred bone screw drilling pathsrelative to one another. More particularly, the central bore 1010, drillguide shaft 1002, and guide bores 1012 a,1012 b, are configured on thedistal end 1004 of the drill guide 1000 such that when the central bore1010 is disposed on the stem 706 of the insertion plate 700 (see FIGS.8d and 8 e), the drill guide shaft 1002 can be rotated on the stem 706into either of two preferred positions in which the guide bores 1012a,1012 b are aligned with the bone screw holes 508 a,508 b or 608 a,608b on either of the flanges 506 or 606. Stated alternatively, in a firstpreferred position (see FIGS. 8d and 8 e), the drill guide 1000 can beused to guide bone screws through the bone screw holes 508 a,508 b inthe flange 506 of the upper element 500, and in a second preferredposition (in which the drill guide is rotated 180 degrees, about thelongitudinal axis of the stem 706, from the first preferred position),the same drill guide 1000 can be used to guide bone screws through thebone screw holes 608 a,608 b in the flange 606 of the lower element 600.When the drill guide 1000 is disposed in either of the preferredpositions, the longitudinal axes of the guide bores 1012 a,1012 b arealigned with the bone screw holes 508 a,508 b or 608 a,608 b on theflanges 506 or 606, and are directed along preferred bone screw drillingpaths through the bone screw holes.

[0079] Accordingly, to secure the upper element flange 506 to the uppervertebral body, the surgeon places the drill guide shaft 1002 onto thestem 706 of the insertion plate 700, and rotates the drill guide 1000into the first preferred position. Preferably, the surgeon then appliesan upward pressure to the drill guide 1000, urging the upper element 500tightly against the endplate of the upper vertebral body. Using asuitable bone drill and cooperating drill bit, the surgeon drills uppertap holes for the upper bone screws. Once the upper tap holes aredrilled, the surgeon rotates the drill guide shaft 1002 on the stem 706of the insertion plate 700 until the guide bores 1012 a,1012 b no longercover the upper bone screw holes 508 a,508 b. The surgeon can then screwthe upper bone screws into the upper tap holes using a suitable surgicalbone screw driver.

[0080] Additionally, to secure the lower element flange 606 to the lowervertebral body, the surgeon further rotates the drill guide shaft 1002on the stem 706 of the insertion plate 700 until the drill guide 1000 isin the second preferred position. Preferably, the surgeon then applies adownward pressure to the drill guide 1000, urging the lower element 600tightly against the endplate of the lower vertebral body. Using thesuitable bone drill and cooperating drill bit, the surgeon drills lowertap holes for the lower bone screws. Once the lower tap holes aredrilled, the surgeon rotates the drill guide shaft 1002 on the stem 706of the insertion plate 700 until the guide bores 1012 a,1012 b no longercover the lower bone screw holes 608 a,608 b. The surgeon can then screwthe lower bone screws into the lower tap holes using the suitablesurgical bone screw driver.

[0081] It should be noted that the bone screws (or other elements of theinvention) may include features or mechanisms that assist in preventscrew backup. Such features may include, but not be limited to, one ormore of the following: titanium plasma spray coating, bead blastedcoating, hydroxylapetite coating, and grooves on the threads.

[0082] Once the elements 500,600 are secured to the adjacent vertebralbones, the surgeon removes the drill guide 1000 from the stem 706 of theinsertion plate 700 and from the treatment area (see FIG. 9a). Using asuitable surgical screw driver, the surgeon then removes the mountingscrews 714 a,714 b that hold the insertion plate 700 against theelements' flanges 506,606, and removes the insertion plate 700 and themounting screws 714 a,714 b from the treatment area (see FIG. 9b).

[0083] Referring now to FIGS. 10a-f, a retaining clip 1150 a of thepresent invention is shown in top (FIG. 10a), lateral (FIG. 10b),posterior (FIG. 10c), anterior (FIG. 10d), postero-lateral perspective(FIG. 10e), and antero-lateral perspective (FIG. 10 f) views. (Thefeatures of retaining clip 1150 a are exemplary of the features of thelike-numbered features of retaining clip 1150 b, which are referenced byb's rather than a's.) Referring now to FIGS. 11a-e, a clip applicator1100 of the insertion instrumentation of the present invention is shownin top (FIG. 11a), lateral (FIG. 11b), and anterior (FIG. 11c) views.FIG. 11d shows a postero-lateral perspective view of the clip applicator1100 holding two retaining clips 1150 a,1150 b of the present invention.FIG. 11e shows an antero-lateral perspective view of FIG. 11d. Referringnow to FIGS. 12a-h, the clip applicator 1100 is shown applying theretaining clips 1150 a,1150 b to the cervical disc replacement device400. FIGS. 12b-h show anterior (FIG. 12b), posterior (FIG. 12c), top(FIG. 12d), bottom (FIG. 12e), lateral (FIG. 12f), antero-lateralperspective (FIG. 12g), and postero-lateral perspective (FIG. 12h) viewsof the cervical disc replacement device 400 after the retaining clips1150 a,1150 b have been applied.

[0084] Once the mounting screws 714 a,714 b and the insertion plate 700are removed, the surgeon uses the clip applicator 1100 to mount theretaining clips 1150 a,1150 b on the flanges 506,606 to assist inretaining the bone screws. As shown in FIGS. 10a-f, each of the clips1150 a,1150 b preferably has an applicator attachment feature (e.g., acentral attachment bore 1152 a,1152 b) and, extending therefrom, a pairof bone screw retaining features (e.g., oppositely directed laterallyextending flanges 1156 a,1156 b and 1158 a,1158 b) and a flangeattachment feature (e.g., an upwardly (or downwardly) extending hookedflange 1160 a,1160 b). The extent of the hook flange 1160 a,1160 b ispreferably formed to bend in toward the base of the hook flange 1160a,1160 b, such that the enclosure width of the formation is wider thanthe mouth width of the formation, and such that the extent is springbiased by its material composition toward the base. The enclosure widthof the formation accommodates the width of the body of a flange 506,606of the cervical disc replacement device 400, but the mouth width of theformation is smaller than the width of the flange 506,606. Accordingly,and referring now to FIGS. 12b-h, each clip 1150 a,1150 b can be appliedto an element flange 506,606 such that the hook flange 1160 a,1160 bgrips the element flange 506,606, by pressing the hook's mouth againstthe edge of the element flange 506,606 with enough force to overcome thebias of the hook flange's extent toward the base, until the flange506,606 is seated in the hook's enclosure. The attachment bore 1152a,1152 b of the clip 1150 a,1150 b is positioned on the clip 1150 a,1150b such that when the clip 1150 a,1150 b is properly applied to theflange 506,606, the attachment bore 1152 a,1152 b is aligned with themounting screw hole 509,609 on the flange 506,606 (see FIGS. 12b-h).Further, the posterior opening of the attachment bore 1152 a,1152 b ispreferably surrounded by a clip retaining features (e.g., a raised wall1162 a,1162 b), the outer diameter of which is dimensioned such that theraised wall 1162 a,1162 b fits into the mounting screw hole 509,609 onthe element flange 506,606. Thus, when the clip 1150 a,1150 b is soapplied to the element flange 506,606, the element flange 506,606 willbe received into the hook's enclosure against the spring bias of thehook's extent, until the attachment bore 1152 a,1152 b is aligned withthe mounting screw hole 509,609, at which time the raised wall 1162a,1162 b will snap into the mounting screw hole 509,609 under the forceof the hook's extent's spring bias. This fitting prevents the clip 1150a,1150 b from slipping off the flange 506,606 under stresses in situ.Each of the laterally extending flanges 1156 a,1156 b and 1158 a,1158 bof the clip 1150 a,1150 b is sized to cover at least a portion of arespective one of the bone screw heads when the clip 1150 a,1150 b isattached in this manner to the flange 506,606 (see FIGS. 12b-h), sothat, e.g., the clips 1150 a,1150 b help prevent the bone screws frombacking out.

[0085] Referring again to FIGS. 11a-e, the clip applicator 1100 has apair of tongs 1102 a,1102 b hinged at a proximal end 1104 of the clipapplicator 1100. Each tong 1102 a,1102 b has an attachment feature(e.g., a nub 1108 a,1108 b) at a distal end 1106 a,1106 b. Each nub 1108a,1108 b is dimensioned such that it can be manually friction lockedinto either of the attachment bores 1152 a,1152 b of the retaining clips1150 a,1150 b. Thus, both clips 1150 a,1150 b can be attached to theclip applicator 1100, one to each tong 1102 a,1102 b (see FIGS. 11d and11 e). Preferably, as shown in FIGS. 11d and 11 e, the clips 1150 a,1150b are attached so that their hook flanges 1154 a,1154 b are directedtoward one another, so that they are optimally situated for attachmentto the element flanges 506,606 of the cervical disc replacement device400 (see FIG. 12a).

[0086] Preferably, the clips 1150 a,1150 b are attached to the clipapplicator 1100 as described above prior to delivery to the surgeon. Theassembly is preferably provided sterile to the surgeon in a blisterpack. Accordingly, when the surgeon is ready to mount the clips 1150a,1150 b to the element flanges 506,606 of the cervical disc replacementdevice 400, the surgeon opens the blister pack and inserts the tongs1102 a,1102 b of the clip applicator 1100 (with the clips 1150 a,1150 battached) into the treatment area.

[0087] Accordingly, and referring again to FIGS. 12a-h, the clips 1150a,1150 b can be simultaneously clipped to the upper 500 and lower 600elements' flanges 506,606 (one to each flange 506,606) using the clipapplicator 1100. More particularly, the mouths of the clips 1150 a,1150b can be brought to bear each on a respective one of the flanges 506,606by manually squeezing the tongs 1102 a,1102 b (having the clips 1150a,1150 b attached each to a set of the distal ends of the tongs 1102a,1102 b) toward one another when the mouths of the clips 1150 a,1150 bare suitably aligned with the flanges 506,606 (see FIG. 12a). Once theclips 1150 a,1150 b have been attached to the flanges 506,660 with theraised walls 1162 a,1162 b fitting into the mounting screw holes 509,609of the flanges 506,606, the clip applicator 1100 can be removed from theclips 1150 a,1150 b by manually pulling the nubs 1108 a,1108 b out ofthe attachment bores 1152 a,1152 b, and the clip applicator 1100 can beremoved from the treatment area.

[0088] After implanting the cervical disc replacement device 400 asdescribed, the surgeon follows accepted procedure for closing thetreatment area.

[0089] Referring now to FIGS. 14a-e, an alternate dual cervical discreplacement device configuration and alternate insertion plates for usetherewith, suitable, for example, for implantation in two adjacentcervical intervertebral spaces, are illustrated in exploded perspective(FIG. 14a), anterior (FIG. 14b), posterior (FIG. 14c), lateral (FIG.14d), and collapsed perspective (FIG. 14e) views. Referring now also toFIGS. 15a-c, an alternate upper element of the configuration is shown inposterior (FIG. 15a), anterior (FIG. 15b), and antero-lateral (FIG. 15c)views. Referring now also to FIGS. 16a-c, an alternate lower element ofthe configuration is shown in posterior (FIG. 16a), anterior (FIG. 16b),and antero-lateral (FIG. 16c) views. Referring now also to FIGS. 17a-c,an alternate, upper, insertion plate of the configuration is shown inanterior (FIG. 17a), posterior (FIG. 17b), and antero-lateral (FIG. 17c)views. Referring now also to FIGS. 18a-c, an alternate, lower, insertionplate of the configuration is shown in anterior (FIG. 18a), posterior(FIG. 18b), and antero-lateral (FIG. 18c) views.

[0090] More particularly, the alternate dual cervical disc replacementdevice configuration 1350 is suitable, for example, for implantationinto two adjacent cervical intervertebral spaces. The configurationpreferably, as shown, includes an alternate, upper, cervical discreplacement device 1400 (including an upper element 1500 and analternate, lower, element 1600), for implantation into an upper cervicalintervertebral space, and further includes an alternate, lower, cervicaldisc replacement device 2400 (including an alternate, upper, element2500 and a lower element 2600), for implantation into an adjacent,lower, cervical intervertebral space. The illustrated alternate, upper,embodiment of the cervical disc replacement device is identical instructure to the cervical disc replacement device 400 described above(and thus like components are like numbered, but in the 1400s ratherthan the 400s, in the 1500s rather than the 500s, and in the 1600srather than the 600s), with the exception that the flange 1606 of thelower element 1600 is configured differently and without bone screwholes. The illustrated alternate, lower, embodiment of the cervical discreplacement device is identical in structure to the cervical discreplacement device 400 described above (and thus like components arelike numbered, but in the 2400s rather than the 400s, in the 2500srather than the 500s, and in the 2600s rather than the 600s), with theexception that the flange 2506 of the upper element 2500 is configureddifferently and without bone screw holes.

[0091] More particularly, in the alternate, upper, cervical discreplacement device 1400 of this alternate configuration, the flange 1606of the lower element 1600 does not have bone screw holes, but has atleast one mounting feature (e.g., a mounting screw hole) 1609 forattaching the lower element 1600 to the alternate, upper, insertionplate 1700 (described below). Similarly, and more particularly, in thealternate, lower, cervical disc replacement device 2400 of thisalternate configuration, the flange 2506 of the upper element 2500 doesnot have bone screw holes, but has at least one mounting feature (e.g.,a mounting screw hole) 2509 for attaching the upper element 2500 to thealternate, lower, insertion plate 2700 (described below). As can be seenparticularly in FIGS. 14a-c, 15 b, 16 b, 17 a, and 18 a, the extent ofthe flange 1606 is laterally offset to the right (in an anterior view)from the midline (and preferably limited to support only the mountingscrew hole 1609), and the extent of the flange 2506 is laterally offsetto the left (in an anterior view) from the midline (and preferablylimited to support only the mounting screw hole 2509), so that theflanges 1606,2506 avoid one another when the alternate lower element1600 of the alternate, upper, cervical disc replacement device 1400, andthe alternate upper element 2500 of the alternate, lower, cervical discreplacement device 2400, are implanted in this alternate configuration(FIGS. 14a-e).

[0092] It should be noted that the alternate, upper, cervical discreplacement device 1400 does not require both elements 1500,1600 to besecured to a vertebral body. Only one need be secured to a vertebralbody, because due to natural compression in the spine pressing theelements' bearing surfaces together, and the curvatures of thesaddle-shaped bearing surfaces preventing lateral, anterior, orposterior movement relative to one another when they are compressedagainst one another, if one element (e.g., the upper element 1500) issecured to a vertebral body (e.g., to the upper vertebral body by bonescrews through the bone screw holes 1508 a,1508 b of the element flange1506), the other element (e.g., the alternate, lower, element 1600)cannot slip out of the intervertebral space, even if that other elementis not secured to a vertebral body (e.g., to the middle vertebral body).Similarly, the alternate, lower, cervical disc replacement device 2400does not require both elements 2500,2600 to be secured to a vertebralbody. Only one need be secured to a vertebral body, because due tonatural compression in the spine pressing the elements' bearing surfacestogether, and the curvatures of the saddle-shaped bearing surfacespreventing lateral, anterior, or posterior movement relative to oneanother when they are compressed against one another, if one element(e.g., the lower element 2600) is secured to a vertebral body (e.g., tothe lower vertebral body by bone screws through the bone screw holes2608 a,2608 b of the element flange 2606), the other element (e.g., thealternate, upper, element 2500) cannot slip out of the intervertebralspace, even if that other element is not secured to a vertebral body(e.g., to the middle vertebral body).

[0093] Accordingly, the alternate, upper, insertion plate 1700 isprovided to facilitate a preferred simultaneous implantation of theupper and lower elements 1500,1600 of the alternate, upper, cervicaldisc replacement device 1400 into the upper intervertebral space.Similarly, the alternate, lower, insertion plate 2700 is provided tofacilitate a preferred simultaneous implantation of the upper and lowerelements 2500,2600 of the alternate, lower, cervical disc replacementdevice 2400 into the lower intervertebral space. The upper and lowerelements 1500,1600 are held by the insertion plate 1700 (preferablyusing mounting screws 1714 a,1714 b) in a preferred relationship to oneanother that is suitable for implantation, identical to the preferredrelationship in which the upper and lower elements 500,600 are held bythe insertion plate 700 as described above. Similarly, the upper andlower elements 2500,2600 are held by the insertion plate 2700(preferably using mounting screws 2714 a,2714 b) in a preferredrelationship to one another that is suitable for implantation, identicalto the preferred relationship in which the upper and lower elements500,600 are held by the insertion plate 700 as described above.

[0094] The illustrated alternate, upper, insertion plate 1700 isidentical in structure to the insertion plate 700 described above (andthus like components are like numbered, but in the 1700s rather than the700s), with the exception that the lower flange 1704 b is offset fromthe midline (to the right in an anterior view) to align its mountingscrew hole 1712 b with the offset mounting screw hole 1609 of thealternate lower element 1600 of the alternate, upper, cervical discreplacement device 1400. Similarly, the illustrated alternate, lower,insertion plate 2700 is identical in structure to the insertion plate700 described above (and thus like components are like numbered, but inthe 2700s rather than the 700s), with the exception that the upperflange 2704 a is offset from the midline (to the left in an anteriorview) to align its mounting screw hole 2712 a with the offset mountingscrew hole 2509 of the alternate upper element 2500 of the alternate,lower, cervical disc replacement device 2400.

[0095] Accordingly, the upper and lower elements 1500,1600, being heldby the insertion plate 1700, as well as the upper and lower elements2500,2600, being held by the insertion plate 2700, can be implantedusing the insertion handle 800, insertion pusher 900, drill guide 1000,clips 1150 a,1150 b (one on the upper element flange 1506, and one onthe lower element flange 2606, because only the upper element 1500 andthe lower element 2600 are secured by bone screws), and clip applicator1100, in the manner described above with respect to the implantation ofthe cervical disc replacement device 400.

[0096] It should be noted that the described alternate configuration(that includes two cervical disc replacement devices) presents thecervical disc replacement devices to the surgeon in a familiar manner.That is, by way of explanation, current cervical fusion surgery involvesplacing a fusion device (e.g., bone or a porous cage) in between theupper and middle cervical intervertebral bones, and in between themiddle and lower vertebral bones, and attaching an elongated two-levelcervical fusion plate to the anterior aspects of the bones. Widely usedtwo-level cervical fusion devices (an example two level fusion plate1350 is shown in anterior view in FIG. 13c and in lateral view in FIG.13d) are configured with a pair of laterally spaced bone screw holes1352 a,1352 b on an upper end 1354 of the plate 1350, a pair oflaterally spaced bone screw holes 1356 a,1356 b on a lower end 1358 ofthe plate 1350, and a pair of laterally spaced bone screw holes 1360a,1360 b midway between the upper and lower ends 1354,1358. To attachthe plate 1350 to the bones, bone screws are disposed through the bonescrew holes and into the corresponding bones. This prevents the bonesfrom moving relative to one another, and allows the bones to fuse to oneanother with the aid of the fusion device.

[0097] Accordingly, as can be seen in FIG. 14b, when the upper and lowerelements 1500,1600 of the cervical disc replacement device 1400, and theupper and lower elements 2500,2600 of the cervical disc replacementdevice 2400, are held in the preferred spatial relationship and alignedfor implantation, the upper element flange 1506 and lower element flange2606, and their bone screw holes 1508 a,1508 b and 2608 a,2608 b,present to the surgeon a cervical hardware and bone screw holeconfiguration similar to a familiar two level cervical fusion plateconfiguration (as described above, a middle pair of bone screws holes isnot needed; however, middle bone screw holes are contemplated by thepresent invention for some embodiments, if necessary or desirable). Themounting of the elements 1500,1600 to the insertion plate 1700 allowsthe elements 1500,1600 to be manipulated as a single unit forimplantation (by manipulating the insertion plate 1700), similar to theway a cervical fusion plate is manipulatable as a single unit forattachment to the bones. Similarly, the mounting of the elements2500,2600 to the insertion plate 2700 allows the elements 2500,2600 tobe manipulated as a single unit for implantation (by manipulating theinsertion plate 2700), similar to the way a cervical fusion plate ismanipulatable as a single unit for attachment to the bones. This aspectof the present invention simplifies and streamlines the cervical discreplacement device implantation procedure.

[0098] While there has been described and illustrated specificembodiments of cervical disc replacement devices and insertioninstrumentation, it will be apparent to those skilled in the art thatvariations and modifications are possible without deviating from thebroad spirit and principle of the invention. The invention, therefore,shall not be limited to the specific embodiments discussed herein.

What is claimed is:
 1. An insertion handle, comprising: a shaft having aproximal end and a distal end; and an engagement member disposed at thedistal end of the shaft and operable to detachably engage an insertionplate that maintains first and second members of an intervertebral discreplacement device in registration with one another for substantiallysimultaneous insertion into an intervertebral disc space of a spinalcolumn.
 2. The insertion handle of claim 1, wherein the shaft isoperable to permit the first and second members of the intervertebraldisc replacement device to be at least one of inserted into and movedwithin the intervertebral disc space without substantially changingtheir orientation with respect to one another.
 3. The insertion handleof claim 1, wherein the insertion handle is detachable from theinsertion plate to facilitate removal of the insertion handle when theintervertebral disc replacement device is positioned within theintervertebral disc space.
 4. The insertion handle of claim 3, wherein:the insertion plate includes a base having a posteriorly directedsurface directed toward the first and second members of theintervertebral disc replacement device, a spaced apart anteriorlydirected surface, and an insertion member extending away from theanteriorly directed surface of the base; and one of the insertion memberof the base and the engagement member of the shaft includes a stem, andthe other of the insertion member of the base and the engagement memberof the shaft includes a bore such that the stem is receivable in thebore and the insertion handle and the insertion plate detachably engageone another.
 5. The insertion handle of claim 4, wherein at least oneof: the stem and the bore are sized and shaped for achieving frictionalengagement; and at least one of the stem and the bore include taperedsurfaces to achieve the frictional engagement.
 6. The insertion handleof claim 4, further comprising an anti-rotational mechanism disposed atat least one of the distal end of the shaft and the stem, theanti-rotational mechanism resisting rotation of the stem within the boreand thereby assisting maintenance of the relative positions of theinsertion handle and the intervertebral disc replacement device whenthey are engaged.
 7. The insertion handle of claim 6, wherein theanti-rotational mechanism includes at least one key element disposed onone of the stem and the bore, and at least one slot element disposed onthe other of the stem and the bore, the at least one key element and theat least one slot element engaging one another when the stem is disposedin the bore in order to resist rotation of the stem within the bore. 8.The insertion handle of claim 7, wherein: the bore is disposedlongitudinally within, and terminates at, the distal end of the shaft;and at least two key elements are disposed at the distal end of theshaft and communicate with the bore such that a diameter of the boreterminating at the distal end of the shaft elastically increases as thestem is urged into the bore to facilitate frictional engagement betweenthe stem and the shaft.
 9. The insertion handle of claim 1, furthercomprising an actuator disposed substantially at the proximal end of theshaft and operable to cause the shaft and the insertion plate todisengage from one another.
 10. The insertion handle of claim 9,wherein: the shaft includes a longitudinal bore extending from theproximal end of the shaft toward the distal end; the insertion handlefurther comprises a pushing member having a proximal end and a distalend and being slideably receivable within the longitudinal bore; andactuation of the proximal end of the pushing member causes the distalend thereof to engage the insertion plate and separate the shaft fromthe insertion plate.
 11. The insertion handle of claim 10, wherein: theinsertion plate includes a base having a posteriorly directed surfacedirected toward the first and second members of the intervertebral discreplacement device, a spaced apart anteriorly directed surface, and aninsertion member extending away from the anteriorly directed surface ofthe base; the insertion member of the base includes a stem and theengagement member of the shaft includes a bore such that the stem isreceivable in the bore to engage the insertion handle and the insertionplate with one another; and actuation of the proximal end of the pushingmember causes the distal end thereof to engage the stem of the insertionplate and separate the shaft from the insertion plate.
 12. The insertionhandle of claim 10, wherein: the proximal end of the shaft includes atleast one first flange and the proximal end of the pushing memberincludes at least one second flange; and respective forces applied tothe first and second flanges facilitates slideable actuation of thepushing member within the longitudinal bore and engagement of the distalend of the pushing member with the stem of the insertion plate toseparate the insertion handle from the insertion plate.
 13. Theinsertion handle of claim 12, wherein the urging of the first and secondflanges towards one another results in the respective forces to causethe insertion handle and the insertion plate to separate from oneanother.
 14. An apparatus for replacing at least a portion of anintervertebral disc in a spinal column, comprising: first and secondmembers of an intervertebral disc replacement device; an insertion platedetachably coupled to each of the first and second members to orientthem for simultaneous insertion into an intervertebral disc spacedefined by respective endplates of first and second vertebral bones ofthe spinal column; and an insertion handle including a shaft having aproximal end and a distal end, and an engagement member disposed at thedistal end of the shaft, the engagement member being operable todetachably engage the insertion plate in order to manipulate the firstand second members such that they may be at least one of inserted intoand moved within the intervertebral disc space without substantiallychanging their orientation with respect to one another.
 15. Theapparatus of claim 14, wherein the apparatus is at least part of asterile assembly disposed in a sealed package.
 16. A method forreplacing at least a portion of an intervertebral disc in a spinalcolumn, comprising the steps of: removing the portion of theintervertebral disc from the spinal column; and manipulating aninsertion handle that is detachably engaged with an insertion plate thatis coupled to first and second members of an intervertebral discreplacement device such that the first and second members may besimultaneously inserted into an intervertebral disc space of the spinalcolumn, wherein the first and second members are engageable with andoperable to permit the vertebral bones to articulate with respect to oneanother.
 17. The method of claim 16, further comprising: manipulatingthe first and second members as a single unit by way of the insertionhandle such that they may be at least one of inserted into and movedwithin the intervertebral disc space without substantially changingtheir orientation with respect to one another.
 18. The method of claim18, further comprising: detaching the insertion handle from theinsertion plate after the first and second members have been positionedwithin the intervertebral disc space.
 19. The method of claim 18,wherein: the insertion handle includes a shaft having a distal end thatis detachably coupled to the insertion plate, and a proximal endcooperating with an actuator that is operable to cause the shaft and theinsertion plate to disengage from one another; and the method includesmanipulating the actuator to cause the distal end of the shaft toseparate from the insertion plate.